The present invention relates to an endoscope apparatus and, more particularly, to an endoscope apparatus having a bending mechanism driven by a motor to bend an insertion section of the endoscope apparatus.
In a conventional endoscope apparatus, an insertion section is manually deflected or bent when the operator controls an angle-knob at a main body (control section) of the endoscope. An endoscope apparatus has been recently developed in which a bending mechanism is driven by a motor. According to conventional endoscope apparatuses having motor-driven bending mechanisms and respectively disclosed in Japanese Utility Model Disclosure Nos. 51-45790 and 51-91989 or Japanese Patent Disclosure No. 56-13455, a flexible tube of the insertion section can be controlled by the ON/OFF state of the motor operated by the operator. Therefore, the flexible tube is bent in accordance with a given torque obtained by the motor which is driven at a given speed. In other words, the flexible tube is bent at a given speed. When the bending speed of a flexible tube inserted into a body cavity is increased, the flexible tube overruns against the will of the operator. The flexible tube may abut against the wall of the body cavity and cause damage to the wall. The bending operation is difficult to perform properly when the bending speed of the flexible tube is high. The operator cannot control the flexible tube under his/her operation. If the bending speed of the flexible tube is decreased, the above problem can be solved, however, the examination becomes time-consuming and inefficient. In the conventional motor-driven endoscope apparatus having an insertion section which is bent at a given speed, an effective and safe endoscopic examination is difficult to perform.
The conventional endoscope apparatus of the type described above has another drawback. It is hard to perform an insertion section-bending operation in a desired manner. The distal end of the insertion section which is inserted in the body cavity undesirably abuts against the wall of the body cavity and continues to be deflected against the wall of the body cavity, so that the surface tissue of the body cavity may be hurt or cut, thus endangering the patient.
In order to solve the above problem, an endoscope apparatus is disclosed in Japanese Utility Model Disclosure No. 51-91990. According to this endoscope apparatus, a friction clutch is disposed between a bending mechanism and a motor. When the distal end of the insertion section contacts the wall of the body cavity of a patient and when a predetermined load is applied to the bending mechanism, the friction clutch slips to prevent an overload from being applied to the wall of the body cavity. However, in the conventional endoscope apparatus of the type described above, if the distal end of the insertion section contacts the inner wall of the body cavity, even when the friction clutch slips to decrease the transmission ratio of the driving force of the motor, a given driving force is still continuously applied to the bending mechanism. As a result, the distal portion of the insertion section continues to be urged against the inner wall of the body cavity, and the patient may feel pain or be hurt. Furthermore, since there is no means for positively signalling the above condition to the operator, the operator may not immediately know of the above condition. The distal end of the insertion section may continue to hurt or cut the inner wall of the body cavity of the patient. Thus, even in the endoscope apparatus of the type described above, a sufficiently effective and safe endoscopic examination cannot be performed.